Search PubMed⌕ Search

Biomedical subjects

J Hilgers

Publications and source records attributed to J Hilgers.

At least 163 records · Page 9Linked to original sources
PubMed1980

Antigenic modulation of mammary tumour virus envelope antigen or GR thymic lymphoma cells in relation to expressions of H-2, TL cell-surface antigens and THY1.

The MLr antigen, a mammary tumour virus-induced antigen on the surface of GR thymic lymphoma cells (GRSL) can be modulated from the cell surface upon incubation with specific antiserum for 1-2 h at 37 degrees C, followed by washing the cells. In contrast, a number of other cell-surface antigens on these GRSL cells cannot be modulated under similar conditions. These antigens include histocompatibility antigens of the H-2 complex (H-2.8 of the K-end and H-2dx(D) of the H-2dx haplotype) and two thymic markers, TL1.2 and Thy1.2. Antigenic modulation of MLr as tested by trypan-blue exclusion and by chromium51 release does not lead to a measurable change in the expression of H-2K, H-2D, TL and Thy1.2 antigens. These results could be confirmed by absorption analysis. The latter analysis showed that the number of antigenic sites per cell are about the same for MLr and the two H-2 antigens, while TL antigens are scarcer and Thy1.2 antigens are more abundant. The procedure of antigenic modulation showed that the MLr antigen resides on MTVgp52, the major protein of the envelope. There was no evidence of internal proteins, such as MTVp27, on the surface of GRSL cells.

Animals↗
PubMed1980

Restriction of C-type viral antigen in H-2/Fv-1 syngeneic mouse somatic cell hybrids.

Somatic cell hybrids between an AKR lymphoma or a C3H sarcoma and H-2, Fv-1 syngeneic CBA sarcoma or carcinoma have been examined for expression of the structural components of murine leukemia virus (MuLV) by radioimmunoassay and complement-dependent cytotoxicity assay. Parental AKR and C3H cells contained high concentrations of MuLV core protein p30 in their cell extracts and showed high sensitivity to anti-MuLVgp70 and p30 sera. In contrast, CBA cells expressed little detectable p30 in the extracts, were much less sensitive to anti-gp70 serum, and were almost insensitive to anti-p30 serum. The hybrids between the AKR or C3H cells and CBA cells had a decreased amount of p30 in the extracts and were almost resistant to cytotoxicity by anti-p30 serum, although they maintained high sensitivity to anti-gp70 serum. These findings suggest that the CBA genotype suppresses the production and cell-surface expression of p30 antigen of AKR and C3H endogenous C-type viruses. The suppressive gene is not Fv-1n.

Animals↗
PubMed1980

Mammary tumor virus antigen expression in inbred mouse strains of European origin established in Japan.

Expression of the mammary tumor virus (MTV) antigen in the milk from inbred mouse strains maintained in Japanese laboratories was investigated by means of the immunodiffusion test (ID) and the results were compared with the incidence of mammary tumors in breeding females of identical strains. Japanese strains tested were classified into two groups. The DD/Tbr, DDD and KF strains were derived from "dd" stock mice, and they showed equally high incidences of MTV antigen expression in the milk, though each strain developed mammary tumors with different incidences; 71%, 14% and 22%, respectively. Other strains originated from Swiss albino mice. The incidence of MTV antigen expression in the milk of SHN and SLN strains was the same as that of mammary tumors at an early age.

Animals↗
PubMed1979

Rigid plasma-membrane-derived vesicles, enriched in tumour-associated surface antigens (MLr), occurring in the ascites fluid of a murine leukaemia (GRSL).

Extracellular membraneous vesicles of GRSL leukaemia cells were isolated from the ascites fluid bathing the cells in vivo, and from cell washes. Mammary tumour virus-induced antigens (MLr) expressed on the surface of the cells are enriched on these vesicles as compared to plasma membranes isolated from the cell homogenate. The lipid fluidity of the vesicles is much smaller than that of the plasma membranes, and the content of the pertinent lipid parameters, cholesterol and sphingomyelin, are accordingly greatly increased. The extracellular vesicles which are also enriched in sialic acid and 5'-nucleotidase are apparently derived from the plasma membrane, probably at least partly by exfoliation of selected parts or domains of the surface of living cells. An analogy between this shedding of vesicles, the formation of endocytotic vesicles and the budding of viruses is noted; all these processes select or assemble rigid lipid domains of the cell membrane. The possible participation of surface microvilli and sub-lethal autolysis in the process of shedding is discussed.

Animals↗
PubMed1979

Identification of a mouse gene required for binding of Rauscher MuLV envelope gp70.

Mouse chromosome segregating somatic cell hybrids were established between a mouse thymic leukemai cell line (GRSL) and Chinese hamster E36 cells. The GRSL cells specifically bound purified Rauscher leukemia virus gp70 while the E36 cells exhibited no binding. The hybrids selectively bound Ruascher gp70 depending on the presence of a mouse cellular gene for the ecotropic murine luekemia gp70 receptor. A syntenic relationship was observed between the DIP-3 chromosome marker (on chromosome 5) and the gp70 receptor in primary clones and subclones of these hybrids; this was confirmed by chromosome analysis. The involvement of H-2 in the binding of Rauscher MuLV gp70 could be ruled out, because discordancies of the receptor presence and H-2 absence as well as of the receptor absence and H-2 presence type could be observed. Our results indicate that the Rec-1 (replication ecotropic MuLV) gene of Gazdar et al. (4) may well be the receptor gene for the ecotropic murine leukemia virus.

Animals↗
PubMed1979

H-2-dependent regulation of the high level of expression of ecotropic murine leukemia virus.

Adult B10.Y mice, which are congenic with C57BL/10ScSn ((B10) mice for the H-2 region, expressed a high titer of infectious ecotropic virus in the spleen. F1 hybrids between B10.Y and B10 mice were negative or had very low levels of virus expression. In (B10.Y x B10)F2 segregant mice, the high virus phenotype segregated with the H-2pa haplotype of B10.Y, whereas the virus-negative phenotype was associated with the H-2b haplotype of B10. Molecular hybridization experiments with a selected ecotropic AKR murine leukemia virus cyclic DNA probe indicated that both partner strains possessed ecotropic virus sequences and that the number of sequences present was the same in B10.Y mice as in B10 mice. This finding excluded the possibility that the H-2-related effect might be due to the presence of additional viral structural genes within or close to the H-2 region of B10.Y mice. The level of expression of this endogenous ecotropic virus was therefore affected by regulatory genes of the H-2 region.

Animals↗
PubMed1979

A radioimmunoassay for virus antibody using binding of 125I-labelled protein A.

An assay for virus antibodies using protein A from Staphylococcus aureus is described. Type B and type C RNA tumour viruses adsorbed on to polystryrene microtitre plate wells were incubated with antiserum and then with 125I-labelled protein A (I-pA) and bound radioactivity was determined. Technical details such as labelling, antigen concentration, storage of I-pA are reported. The specificity of the reaction was investigated in detail by competition experiments with purified unbound homologous viruses. This assay also proved to be sensitive for demonstration of autogenous immunity to both type B and type C RNA tumour viruses. A study using antisera against purified core and envelope virus proteins of mammary tumour and leukaemis viruses suggested that the reaction mainly involves surface antigens of the intact virions.

Animals↗
PubMed1979

Impaired maturation of mouse mammary tumor virus precursor polypeptides in lymphoid leukemia cells, producing intracytoplasmic A particles and no extracellular B-type virions.

Processing of polypeptides of the mouse mammary tumor virus, a type B retrovirus, was investigated in a transplanted thymic lymphoma cell line of the GR strain (GRSL). This cell line was maintained in vivo in ascites form and in vitro as a suspension culture. GRSL cells produce clusters of intracytoplasmic A particles and are virtually deficient in the production of mature extracellular B-type particles. As control, a mammary tumor cell line of the same mouse strain capable of complete virion synthesis was used. The kinetics of viral polypeptide synthesis were studied by pulse labeling with various isotopes (including (35)S and (32)P), followed by immunoprecipitation of cell lysates with monospecific antisera to the major mouse mammary tumor virus gag and env proteins, p27 and gp52, respectively. Both the primary gag and env precursor polypeptides were synthesized in the GRSL cells, but their conversion into viral proteins was impaired. The major gag precursor, Pr73(gag), was stable over a period of 8 h, and mature viral core polypeptides could not be detected. Also, the highly phosphorylated intermediates in the proteolytic processing of Pr73(gag) in virus-producing cells were absent in GRSL cells. By immunoprecipitation, Pr73(gag) was detected in a GRSL particle fraction with the density of intracytoplasmic A particles. The precursor for envelope proteins, Pr73(env), was turned over without the generation of mature viral envelope components gp52 and gp36. The in vivo-transplanted ascites GRSL cells, however, were shown to express gp52 on the cell surface together with a 73,000-dalton polypeptide, as indicated by cell surface iodination and immunoprecipitation.

Animals↗
PubMed1978

Membrane fluidity, capping of cell-surface antigens and immune response in mouse leukaemia cells.

Transplantation of primary GRSL cells in the ascitic form led to a decrease in membrane microviscosity as measured by the fluorescence polarization technique. The transplanted GRSL ascitic cells showed a markedly lower ability to form caps with respect to both virus-related (MLr, GIX) and normal (H-2.7(G), H-2.8(K) and TL1.2) cell-surface antigens and their appropriate antisera in the indirect membrane immunofluorescence tests, than did primary GRSL cells, transplanted GRSL cells growing in solid form, and thymocytes, which all exhibited significantly higher membrane microviscosities. Transplantation of primary GRSL cells into syngeneic mice pre-irradiated with 400 rad did not lead to a fall in membrane microviscosity. It is suggested that the host immune response in intact mice leads to a selective survival of ascitic tumour cells with low membrane microviscosity.

Animals↗
PubMed1978

Immune response-associated antigens on mouse leukemia cells. I. Detection of Ia antigens on GRSL cells.

The expression of immune response-associated (Ia) antigens on the surface of mouse strain GR (H-2dx) ascites leukemia (GRSL) cell lines was studied by cytotoxic tests, immunofluorescence, and immunoprecipitation assays. Ia expression varied among the three GRSL cells lines (GRSL 2, GRSL 14, and GRSL 15) studied by cytotoxic assay. GRSL 14 cells showed the strongest expression of Ia antigens among these three cell lines. A time-course study of tumor growth in mice revealed that Ia antigens on the tumor cells demonstrated the strongest expression 10 days after injection of GRSL cells into GR mice, and that subsequently it decreased until the death of the animal. Cells treated with neuraminidase exhibited more readily detectable Ia antigens, expecially in the late stages of leukemia, which suggested that Ia antigens had been masked by sialic acid. Immunoprecipitation studies revealed that Ia molecules on the leukemia cell had the same molecular weight as those on the normal lymphocytes. Immunofluorescence studies disclosed that Ia antigens were distributed diffusely on the surface of the tumor cells.

Animals↗
PubMed1978

Immune response-associated antigens on mouse leukemia cells. II. Anti-Ia sera inhibit the MLR reaction between normal GR spleen cells and syngeneic spleen cells of GRSL tumor-bearing mice.

Mitomycin C-treated ascites cells of Ia antigen-positive GRSL14 tumor cells and spleen cells from GRSL14 tumor-bearing mice stimulated lymphocyte proliferative responses in normal syngeneic GR spleen cells. Furthermore, mitomycin C-treated T cells purified from spleen cells of tumor-bearing mice also stimulated normal GR spleen cells. Anti-Ia sera inhibited the stimulating ability of tumor cells and of spleen cells of tumor-bearing mice. These data suggest a role for I region gene products in immune surveillance for syngeneic tumors.

Animals↗
PubMed1978

Interferon treatment of NZB mice: accelerated progression of autoimmune disease.

The effect of long-term administration of interferon in New Zealand Black and New Zealand Black/New Zealand White F1 hybrid mice was studied. Treatment with moderate doses of interferon (10(4) units, five times weekly for 8 weeks) did not depress murine leukemia virus gp69/71 levels in serum and spleen, nor p30 levels in the spleen. Interferon given at 10(5.1) units (three times weekly for 37 weeks) caused an increased incidence of anti-erythrocyte antibodies in New Zealand Black mice. Finally, the hybrid mice given interferon at 10(6.0) units (three times weekly for 33 weeks) had increased renal immune complex deposits and increased incidences of proteinuria and anemia.

Anemia, Hemolytic↗
PubMed1977

Levels of mammary tumor virus in hormone-dependent and -independent mouse mammary tumor cells.

Levels of mammary tumor virus particles (types A and B) and levels of the virus antigen were assayed in hormone-dependent and -independent mammary tumors of GR mice. Various transplant generations of seven separate tumor lines were investigated. The results indicated that the tumors consisted of different cell clones, each of which exhibited a separate progressive expression and subsequent loss of the mammary tumor virus. When the tumors were transplanted, levels of B particles first declined in the hormone-dependent cells, but in later transplant generations, the B particle content of the autonomous cells also dropped. In some tumor lines, this was accompanied by a decrease in viral antigens and/or A particles, but in other lines these concentrations remained high. One tumor line (line V) that remained hormone-dependent throughout nine transplantations was practically devoid of B particles but contained high levels of A particles and mammary tumor antigen.

Animals↗
PubMed1976

In vitro transforming activity of EBV. I-Establishment and properties of two EBV strains (M81 and M72) produced by immortalized Callithrix jacchus lymphocytes.

In vitro transformation of Callithrix jacchus marmoset lymphocytes was achieved with a nasopharyngeal carcinoma (NPC) derived Epstein-Barr virus (EBV) strain, HKLY-28. Two permanent and virus producing lymphoblastoid cell lines, M81 and M72, were obtained. Comparison between the original HKLY-28 line and both M81 and M72 lines showed that passage in the marmosets lymphocytes greatly enhanced viral production and transforming activity of the virus as observed in cottontop derived B95.8 lymphoblastoid line.

Animals↗